Effect of Cadmium on Trophoblast Cell Proliferation and Apoptosis in Different Gestation Periods of Rat Placenta

Dietary Supplementation with Rumen-Protected Arginine or N-Carbamylglutamate Enhances Fetal Liver Development in Nutrient-Restricted Pregnant Hu Ewes

This study was conducted in nutrient-restricted pregnant Hu ewes to determine whether rumen-protected arginine (RP-Arg) or N-carbamylglutamate (NCG) supplementation affects fetal liver growth and development. From 35 d to 110 d of gestation, 32 Hu ewes were randomly divided into four groups: a control group (100% of the National Research Council (NRC) requirements), a nutrient-restricted group (50% of the NRC requirements), and two treatment groups (ARG and NCG, 50% of the NRC requirements, supplemented with 20 g/day RP-Arg or 5 g/day NCG, respectively). Fetal body weights, fetal liver growth performance, the capability of antioxidation, and the expression of the mRNA and proteins of apoptosis-related genes in the fetal liver were determined and analyzed at 110 d of gestation. The dry matter, water, fat, protein, and ash components of the fetal livers in the RG group were found to be lower than in the CG group, and these components were significantly higher in the NCG group than in the RG group (p < 0.05). A decrease in DNA, RNA, and protein concentrations and contents, as well as in protein/DNA ratios, was observed in the RG group in comparison to the CG group (p < 0.05). Compared with the RG group, the NCG group had higher concentrations of DNA, RNA, and protein, as well as higher protein/DNA ratios (p < 0.05). The RG group had lower concentrations of cholinesterase, nitric oxide, nitric oxide synthase, superoxide dismutase, alanine aminotransferase, and total protein than the CG group (p < 0.05). The RG group had higher levels of glutathione peroxidase, maleic dialdehyde, and aspartate aminotransferase than the CG group (p < 0.05). In the RG group, the mRNA and protein expression of p53 and Bax was significantly increased (p < 0.05) compared with the CG group, and the gene expression of FasL and Bcl-2, the ratio of Bcl-2 to Bax, and the protein expression of Bcl-2 in the RG group were lower (p < 0.05) than in the CG group. It appears that RP-Arg and NCG supplementation during pregnancy could influence fetal liver growth and development. A nutrition-based therapeutic intervention to alleviate reduced fetal growth can be developed based on this study, which has demonstrated that maternal undernutrition during pregnancy induces the maldevelopment of the fetal liver.

Fetoplacental Disposition and Toxicity of Cadmium in Mice Lacking the Bcrp Transporter

The environmental toxicant cadmium (Cd) impairs the growth of rodents and humans in utero which in turn heightens susceptibility to diseases later in life. We previously demonstrated that the maternal-facing efflux transporter, breast cancer resistance protein (human BCRP/ABCG2, mouse Bcrp/Abcg2) confers resistance against Cd toxicity in human trophoblasts. In the current study, we sought to determine whether the absence of Bcrp alters the fetoplacental disposition and toxicity of Cd in mice. Pregnant female wild-type (WT) and Bcrp-null mice (n = 9-10/group) were administered a single injection of saline (5 ml/kg) or CdCl2 (5 mg/kg) on gestational day (GD) 9. Following Cd treatment, Bcrp-null offspring were shorter and accumulated more Cd in their placentas on GD 17 compared to WT mice. Because Cd can adversely impact placentation and transplacental nutrient delivery in mice, multiple pathways were assessed using morphometrics and immunohistochemistry including placenta zonation, vasculature development, and nutrient transporter expression. Most notably, the placentas of Bcrp-null mice had reduced immunostaining of the cell adhesion marker, β-catenin, and the trophoblast marker, cytokeratin, as well as decreased expression of divalent metal nutrient transporters (Dmt1, Zip14, and ZnT1) following Cd treatment. In summary, the absence of Bcrp expression increased placental concentrations of Cd which was associated with shorter fetal size that may be related to differential changes in molecular patterns of placental development and nutrition.

Cadmium reduces growth of male fetuses by impairing development of the placental vasculature and reducing expression of nutrient transporters

In utero exposure to the toxic metal cadmium (Cd) alters fetoplacental growth in rodents and has been inversely associated with birth weight and infant size in some birth cohorts. Moreover, studies suggest that Cd may have differential effects on growth and development according to offspring sex. The purpose of the current study was to evaluate changes in male and female fetoplacental development following a single injection of saline (5 ml/kg ip) or cadmium chloride (CdCl2, 2.5, 5 mg/kg, ip) on gestational day (GD) 9. By GD18, no changes in fetal or placental weights were observed after treatment with 2.5 mg/kg CdCl2. By comparison, the weight and length of male fetuses and their placentas were reduced following treatment with 5 mg/kg CdCl2 whereas no change was observed in females. In addition, the area of maternal and fetal blood vessels as well as the expression of the glucose transporters, Glut1 and Glut3, and the endothelial marker, CD34, were reduced in the placentas of CdCl2-treated male offspring compared to females. Interestingly, the placentas of females accumulated 80% more Cd than males after CdCl2 (5 mg/kg) administration. Female placentas also had higher concentrations of zinc and the zinc transporter Znt1 compared to males which may explain the limited changes in fetal growth observed following CdCl2 treatment. Taken together, disruption of vasculature development and reduced expression of glucose transporters in the placenta provide potential mechanisms underlying reduced fetal growth in male offspring despite the greater accumulation of Cd in female placentas.

LncRNA Tuna is activated in cadmium-induced placental insufficiency and drives the NRF2-mediated oxidative stress response

Cadmium (Cd) is a toxic heavy metal found throughout the environment and one of the top ten toxicants of major public health concern identified by the World Health Organization. In utero Cd exposure causes fetal growth restriction, malformation, and spontaneous abortion; however, the mechanisms by which Cd impacts these outcomes are poorly understood. Cd accumulates in the placenta, suggesting that these negative outcomes may be a consequence of disrupted placental function and placental insufficiency. To understand the impact of Cd on gene expression within the placenta, we developed a mouse model of Cd-induced fetal growth restriction through maternal consumption of CdCl2 and performed RNA-seq on control and CdCl2 exposed placentae. The top differentially expressed transcript was the Tcl1 Upstream Neuron-Associated (Tuna) long non-coding RNA, which was upregulated over 25-fold in CdCl2 exposed placentae. Tuna has been shown to be critical for neural stem cell differentiation. However, within the placenta, there is no evidence that Tuna is normally expressed or functional at any developmental stage. To determine the spatial expression of Cd-activated Tuna within the placenta, we used in situ hybridization as well as placental layer-specific RNA isolation and analysis. Both methods confirmed the absence of Tuna expression in control samples and determined that Cd-induced Tuna expression is specific to the junctional zone. Since many lncRNAs regulate gene expression, we hypothesized that Tuna forms part of the mechanism of Cd-induced transcriptomic changes. To test this, we over-expressed Tuna in cultured choriocarcinoma cells and compared gene expression profiles to those of control and CdCl2 exposed cells. We demonstrate significant overlap between genes activated by Tuna overexpression and genes activated by CdCl2 exposure, with enrichment in the NRF2-mediated oxidative stress response. Herein we analyze the NRF2 pathway and show that Tuna increases NRF2/NRF2 both at the transcript and protein levels. Tuna drives increased NRF2 target gene expression, a result that is abrogated with the use of an NRF2 inhibitor, confirming that Tuna activates oxidative stress response genes through this pathway. This work identifies the lncRNA Tuna as a potential novel player in Cd-induced placental insufficiency.

Protective role of the placental efflux transporter BCRP/ABCG2 in the relationship between prenatal cadmium exposure, placenta weight, and size at birth

BACKGROUND AND AIM

Placental efflux transporter proteins, such as BCRP, reduce the placental and fetal toxicity of environmental contaminants but have received little attention in perinatal environmental epidemiology. Here, we evaluate the potential protective role of BCRP following prenatal exposure to cadmium, a metal that preferentially accumulates in the placenta and adversely impacts fetal growth. We hypothesized that individuals with a reduced function polymorphism in ABCG2, the gene encoding BCRP, would be most vulnerable to the adverse impacts of prenatal cadmium exposure, notably, smaller placental and fetal size.

METHODS

We measured cadmium in maternal urine samples at each trimester and in term placentas from UPSIDE-ECHO study participants (NY, USA; n = 269). We fit adjusted multivariable linear regression and generalized estimating equation models to examine log-transformed urinary and placental cadmium concentrations in relation to birthweight, birth length, placental weight, and fetoplacental weight ratio (FPR) and stratified models by ABCG2 Q141K (C421A) genotype.

RESULTS

Overall 17% of participants expressed the reduced-function ABCG2 C421A variant (AA or AC). Placental cadmium concentrations were inversely associated with placental weight (β = -19.55; 95%CI: -37.06, -2.04) and trended towards higher FPR (β = 0.25; 95%CI: -0.01, 0.52) with stronger associations in 421A variant infants. Notably, higher placental cadmium concentrations in 421A variant infants were associated with reduced placental weight (β = -49.42; 95%CI: 98.87, 0.03), and higher FPR (β = 0.85, 95%CI: 0.18, 1.52), while higher urinary cadmium concentration was associated with longer birth length (β = 0.98; 95%CI: 0.37, 1.59), lower ponderal index (β = -0.09; 95%CI: 0.15, -0.03), and higher FPR (β = 0.42; 95%CI: 0.14, 0.71).

CONCLUSIONS

Infants with reduced function ABCG2 polymorphisms may be particularly vulnerable to the developmental toxicity of cadmium as well as other xenobiotics that are BCRP substrates. Additional work examining the influence of placental transporters in environmental epidemiology cohorts is warranted.

Attenuating effects of selenium and zinc against hexavalent chromium-induced oxidative stress, hormonal instability, and placenta damage in preimplanted rats

As a toxic metal, hexavalent chromium (CrVI) has effects on both the reproductive and endocrine systems. This study aimed to evaluate the protective effects of selenium (Se) and zinc (Zn) against the toxicity of chromium on the placenta in pregnant Wistar albino rats. Thirty pregnant Wistar rats were divided into control and four treated groups, receiving subcutaneously (s.c) on the 3rd day of pregnancy, K₂Cr₂O₇ (10 mg/kg body weight (bw)) alone, or in association with Se (0.3 mg/kg bw), ZnCl₂ (20 mg/kg bw), or both of them simultaneously. Plasma steroid hormones, placenta histoarchitecture, oxidative stress profile, and developmental parameters were investigated. These results showed that K₂Cr₂O₇ exposure induced a significant increase in the levels of both plasma estradiol (E₂) and placenta malondialdehyde (MDA), the number of fetal resorptions, and percent of post-implantation loss. On the other hand, K₂Cr₂O₇ significantly reduced developmental parameters, maternal body and placenta weight, and plasma progesterone (P) and chorionic gonadotropin hormone (β HCG) levels. However, K₂Cr₂O₇ significantly decreased the placenta activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), and nonprotein sulfhydryl (NPSH). These changes have been reinforced by histopathological evaluation of the placenta. Se and/or ZnCl₂ supplementation provoked a significant improvement in most indices. These results suggest that the co-treatment with Se or ZnCl₂ strongly opposes the placenta cytotoxicity induced by K₂Cr₂O₇ through its antioxidant action.

Resveratrol ameliorates toxic effects of cadmium on placental development in mouse placenta and human trophoblast cells

BACKGROUND

Cadmium (Cd) is a common heavy metal pollutant. Prenatal exposure to Cd results in adverse effects on fetal development. Placental apoptosis, inflammation, and epigenetic disruption have been implicated in Cd-induced placental toxicity. Resveratrol (Res) is a naturally occurring polyphenol with anti-apoptotic, anti-inflammatory, and epigenetic regulatory activities. In present study, the effects of Res on placental toxicity induced by Cd were evaluated.

METHODS

Pregnant CD-1 mice were fed with base diet containing 0.2% Res started on gestational day 0 (GD0), and intraperitoneally injected with 4.5 mg/kg CdCl₂ or saline once on GD9. JEG-3 cells were treated with 20 μM Res for 24 hr in the absence or presence of 20 μM CdCl₂ for the second 12 hr. The fetal outcomes, the apoptosis in placenta and JEG-3 cells, the expression of inflammatory cytokines and chemokines including tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-γ), monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein-2 (MIP-2) and chemokine (C-X-C motif) ligand 1 (KC), and expression of endoplasmic reticulum (ER) stress markers were evaluated. The expression and activities of DNA methyltransferase (DNMT), and the activation of Akt signaling pathway were detected.

RESULTS

Cd exposure resulted in decreased fetal weight and crown-rump length while Res ameliorated these outcomes. Res suppressed Cd-induced apoptosis in placenta and JEG-3 cells, and decreased Cd-induced expression of TNF-α, IFN-γ, MCP-1, MIP-2, and KC in placenta. Cd greatly increased ER stress in placenta in mice, which was partially ameliorated by Res treatment. Res decreased Cd-induced upregulation of DNMT activity and suppressed Cd-induced expression of DNMT3B. Res restored estradiol secretion, enhances activity and protein levels of SIRT1 and inhibited Cd-induced activation of Akt signaling pathway.

CONCLUSION

Res ameliorated Cd-induced placental toxicity and regulated DNMT3 expression and PI3K/Akt pathway activation.

Increased expression of apoptotic markers in human full-term placenta after exposure to elevated environmental cadmium levels during pregnancy

Cadmium (Cd), a toxic heavy metal, produces various forms of environmental contaminations and health problems in human. In this study, we aimed to examine the localization of several apoptotic markers in human placentas from pregnant women who were environmentally exposed to Cd. Twelve pregnant women participated in this analysis and they were divided into 2 groups according to their living areas: high-Cd (H-Cd) and low-Cd (L-Cd) groups. After delivery, the placentas were immediately harvested, and the placental width, length, and weight were measured. The placental Cd concentration was determined by using ICP-MS. The expression of three apoptotic markers, cleaved caspase-3, cleaved lamin A/C, and TUNEL, was examined in immunohistochemistry. In results, the placental Cd concentration in the H-Cd group was higher than that in the L-Cd group. In contrast, a significant decrease in the BW (birth weight):PW (placenta weight) ratio representing the placental nutrient transport function was found in the H-Cd group, and an inverse correlation between placental Cd concentration and BW:PW ratio was demonstrated. Additionally, significant elevations in the expression of cleaved caspase-3, cleaved lamin A/C proteins, and TUNEL were shown in the H-Cd placenta. Moreover, positive correlations were found between the placental Cd concentration and the expression of cleaved caspase-3 and TUNEL. Collectively, our findings suggest that the exposure of pregnant women to environmental Cd might induce Cd to be transferred to the body and then accumulated in the placenta, resulting in disturbance of the placental function and eventual apoptosis.

Comparing the Predictivity of Human Placental Gene, microRNA, and CpG Methylation Signatures in Relation to Perinatal Outcomes

Molecular signatures are being increasingly integrated into predictive biology applications. However, there are limited studies comparing the overall predictivity of transcriptomic vs. epigenomic signatures in relation to perinatal outcomes. This study set out to evaluate mRNA and microRNA (miRNA) expression and cytosine-guanine dinucleotide (CpG) methylation signatures in human placental tissues and relate these to perinatal outcomes known to influence maternal/fetal health; namely, birth weight, placenta weight, placental damage, and placental inflammation. The following hypotheses were tested: (1) different molecular signatures will demonstrate varying levels of predictivity towards perinatal outcomes, and (2) these signatures will show disruptions from an example exposure (i.e., cadmium) known to elicit perinatal toxicity. Multi-omic placental profiles from 390 infants in the Extremely Low Gestational Age Newborns cohort were used to develop molecular signatures that predict each perinatal outcome. Epigenomic signatures (i.e., miRNA and CpG methylation) consistently demonstrated the highest levels of predictivity, with model performance metrics including R^2 (predicted vs. observed) values of 0.36-0.57 for continuous outcomes and balanced accuracy values of 0.49-0.77 for categorical outcomes. Top-ranking predictors included miRNAs involved in injury and inflammation. To demonstrate the utility of these predictive signatures in screening of potentially harmful exogenous insults, top-ranking miRNA predictors were analyzed in a separate pregnancy cohort and related to cadmium. Key predictive miRNAs demonstrated altered expression in association with cadmium exposure, including miR-210, known to impact placental cell growth, blood vessel development, and fetal weight. These findings inform future predictive biology applications, where additional benefit will be gained by including epigenetic markers.

Increased apoptosis, reduced Wnt/β-catenin signaling, and altered tail development in zebrafish embryos exposed to a human-relevant chemical mixture

A wide variety of anthropogenic chemicals is detected in humans and wildlife and the health effects of various chemical exposures are not well understood. Early life stages are generally the most susceptible to chemical disruption and developmental exposure can cause disease in adulthood, but the mechanistic understanding of such effects is poor. Within the EU project EDC-MixRisk, a chemical mixture (Mixture G) was identified in the Swedish pregnancy cohort SELMA by the inverse association between levels in women at around gestational week ten with birth weight of their children. This mixture was composed of mono-ethyl phthalate, mono-butyl phthalate, mono-benzyl phthalate, mono-ethylhexyl phthalate, mono-isononyl phthalate, triclosan, perfluorohexane sulfonate, perfluorooctanoic acid, and perfluorooctane sulfonate. In a series of experimental studies, we characterized effects of Mixture G on early development in zebrafish models. Here, we studied apoptosis and Wnt/β-catenin signaling which are two evolutionarily conserved signaling pathways of crucial importance during development. We determined effects on apoptosis by measuring TUNEL staining, caspase-3 activity, and acridine orange staining in wildtype zebrafish embryos, while Wnt/β-catenin signaling was assayed using a transgenic line expressing an EGFP reporter at β-catenin-regulated promoters. We found that Mixture G increased apoptosis, suppressed Wnt/β-catenin signaling in the caudal fin, and altered the shape of the caudal fin at water concentrations only 20-100 times higher than the geometric mean serum concentration in the human cohort. These findings call for awareness that pollutant mixtures like mixture G may interfere with a variety of developmental processes, possibly resulting in adverse health effects.

α-Solanine Causes Cellular Dysfunction of Human Trophoblast Cells via Apoptosis and Autophagy

The trophoblast, an embryonic tissue, exerts a crucial role in the processes of implantation and placentation. Toxins in food can cause malfunction of trophoblasts, resulting in apoptosis, oxidative stress, and abnormal angiogenesis. α-solanine, a steroidal glycoalkaloid, has antitumor properties on several cancer cells. However, its effect on human trophoblasts has not been elucidated. In this study, human extravillous trophoblast HTR-8/SVneo cells were exposed to α-solanine. Cellular functions including proliferation, migration, invasion, tube formation, and apoptosis were assessed. To monitor autophagic flux, trophoblasts were transfected with a mCherry-GFP-LC3B vector using lentiviral transduction, and expression of autophagy-related biomarkers including Beclin 1, Atgl3, and microtubule-associated protein 1 light chain-3 (MAP1-LC3) were detected. The results show that application of 20 μM α-solanine or above inhibited the cell viability, migration, invasion, and tube formation of the human trophoblast. Cell cycle was arrested at S and G2/M phases in response to 30 μM α-solanine. α-solanine induced apoptosis of HTR-8/SVneo cells and triggered autophagy by increasing the autophagic gene expression and stimulating the formation of autophagosome and autophagic flux. In conclusion, α-solanine can impair the functions of human trophoblast cells via activation of cell apoptosis and autophagy.

Comprehensive Review of Cadmium Toxicity Mechanisms in Male Reproduction and Therapeutic Strategies

Cadmium (Cd) has been widely studied as an environmental pollutant for many years. Numerous studies have reported that Cd exposure causes damage to the heart, liver, kidneys, and thyroid in vivo. The emerging evidence suggests that Cd exposure induces damage on male reproductive system, which is related to oxidative stress, inflammation, steroidogenesis disruption, and epigenetics. Current preclinical animal studies have confirmed a large number of proteins and intracellular signaling pathways involved in the pathological process of Cd-induced male reproductive damage and potential measures for prophylaxis and treatment, which primarily include antioxidants, anti-inflammatory agents, and essential ion supplement. However, explicit pathogenesis and effective treatments remain uncertain. This review collects data from the literatures, discusses the underlying mechanisms of Cd-induced toxicity on male reproductive function, and summarizes evidence that may provide guidance for the treatment and prevention of Cd-induced male reproductive toxicity.

Human placental cell line HTR-8/SVneo accumulates cadmium by divalent metal transporters DMT1 and ZIP14

Cadmium (Cd) is a global pollutant that accumulates in the placenta and can cause placental dysfunction. Although iron transporters have been suggested to participate in placental Cd uptake, it is still unknown which transporters are actually involved in this process. We specifically aimed to study the role of three iron transporters in the uptake of Cd into the placental cell line HTR-8/SVneo. For this purpose, Divalent Metal Transporter (DMT)1 and ZRT/IRT like protein (ZIP)8 and ZIP14 were downregulated and changes in cellular Cd levels analysed in relation to controls. As clearly shown by the reduction of the Cd content by ∼60% in DMT1- and ZIP14-downregulated cells, the two proteins are essential for Cd accumulation in HTR-8/SVneo cells. Using a validated antibody, we show DMT1 to be localised in situ in trophoblast and stromal cells. We further wanted to investigate how placental cells cope with Cd loading and which metallothionein (MT) isoforms they express. Cd-exposed cells accumulate Cd in a dose-dependent manner and upregulate MT2A accordingly (up to 15-fold induction upon 5 μM CdCl₂ treatment for 72 h). 5 μM Cd exposure for 72 h decreased cell number to 60%, an effect that was aggravated by MT2A depletion (cell number reduced to 30%) indicating additive effects. In conclusion, our data suggest that DMT1 and ZIP14 are required for Cd uptake into human placental cells that upregulate MT2A to store and detoxify the metal. Cd storage in the placenta reduces Cd transport to the fetus, which, however, could impair placental functions and fetal development.

In Vitro Effects of Titanium Dioxide Nanoparticles (TiO2NPs) on Cadmium Chloride (CdCl2) Genotoxicity in Human Sperm Cells

The environmental release of titanium dioxide nanoparticles (TiO₂NPs) associated with their intensive use has been reported to have a genotoxic effect on male fertility. TiO₂NP is able to bind and transport environmental pollutants, such as cadmium (Cd), modifying their availability and/or toxicity. The aim of this work is to assess the in vitro effect of TiO₂NPs and cadmium interaction in human sperm cells. Semen parameters, apoptotic cells, sperm DNA fragmentation, genomic stability and oxidative stress were investigated after sperm incubation in cadmium alone and in combination with TiO₂NPs at different times (15, 30, 45 and 90 min). Our results showed that cadmium reduced sperm DNA integrity, and increased sperm DNA fragmentation and oxidative stress. The genotoxicity induced by TiO₂NPs-cadmium co-exposure was lower compared to single cadmium exposure, suggesting an interaction of the substances to modulate their reactivity. The Quantitative Structure-Activity Relationship (QSAR) computational method showed that the interaction between TiO₂NPs and cadmium leads to the formation of a sandwich-like structure, with cadmium in the middle, which results in the inhibition of its genotoxicity by TiO₂NPs in human sperm cells.

Identification of environmental chemicals targeting miscarriage genes and pathways using the comparative toxicogenomics database

BACKGROUND

Miscarriage is a prevalent public health issue and many events occur before women are aware of their pregnancy, complicating research design. Thus, risk factors for miscarriage are critically understudied. Our goal was to identify environmental chemicals with a high number of interactions with miscarriage genes, based on known toxicogenomic responses.

METHODS

We used miscarriage (MeSH: D000022) and chemical gene lists from the Comparative Toxicogenomics Database in human, mouse, and rat. We assessed enrichment for gene ontology biological processes among the miscarriage genes. We prioritized chemicals (n = 25) found at Superfund sites or in the blood or urine pregnant women. For chemical-disease gene sets of sufficient size (n = 13 chemicals, n = 20 comparisons), chi-squared enrichment tests and proportional reporting ratios (PRR) were calculated. We cross-validated enrichment results.

RESULTS

Miscarriage was annotated with 121 genes and overrepresented in inflammatory response (q = 0.001), collagen metabolic process (q = 1 × 10-13), cell death (q = 0.02), and vasculature development (q = 0.005) pathways. The number of unique genes annotated to a chemical ranged from 2 (bromacil) to 5607 (atrazine). In humans, all chemicals tested were highly enriched for miscarriage gene overlap (all p < 0.001; parathion PRR = 7, cadmium PRR = 6.5, lead PRR = 3.9, arsenic PRR = 3.5, atrazine PRR = 2.8). In mice, highest enrichment (p < 0.001) was observed for naphthalene (PRR = 16.1), cadmium (PRR = 12.8), arsenic (PRR = 11.6), and carbon tetrachloride (PRR = 7.7). In rats, we observed highest enrichment (p < 0.001) for cadmium (PRR = 8.7), carbon tetrachloride (PRR = 8.3), and dieldrin (PRR = 5.3). Our findings were robust to 1000 permutations each of variable gene set sizes.

CONCLUSION

We observed chemical gene sets (parathion, cadmium, naphthalene, carbon tetrachloride, arsenic, lead, dieldrin, and atrazine) were highly enriched for miscarriage genes. Exposures to chemicals linked to miscarriage, and thus linked to decreased probability of live birth, may limit the inclusion of fetuses susceptible to adverse birth outcomes in epidemiology studies. Our findings have critical public health implications for successful pregnancies and the interpretation of adverse impacts of environmental chemical exposures on pregnancy.

Concentrations of bisphenol A and its alternatives in paired maternal-fetal urine, serum and amniotic fluid from an e-waste dismantling area in China

Bisphenol A (BPA) and its alternatives are suspected endocrine disruptors. However, prenatal exposure and transplacental transfer of bisphenols (BPs is still limited. Therefore, BPA and its six alternatives in maternal serum (MS), maternal urine (MU), cord serum (CS), and amniotic fluid (AF) samples collected from 106 maternal-fetal pairs in an e-waste dismantling site in Southern China were determined. Bisphenol AF (BPAF) and bisphenol S (BPS) were the dominant BPA alternatives observed in MS and CS, and the geometric mean (GM) concentration of BPAF (0.013 ng/mL in MS, 0.097 ng/mL in CS) and BPS (0.01 ng/mL in MS, 0.03 ng/mL in CS) in MS and CS was lower than that of BPA (0.5 ng/mL in MS, 1.2 ng/mL in CS). The ratios of BPA concentrations between MU and MS (MU:MS ratio) were over three times higher than those of AF and CS (AF:CS ratio), thereby suggesting low biotransformation/metabolism of BPA in fetuses. The placental transfer rates of BPs (i.e., CS:MS ratio) were compound-specific (BPAF 3.26, BPA 1.94, BPS 1.11). Results suggest that BPA and its alternatives can pass through the placental barrier. The placental transfer rates of BPs are positively related to molecular weight or log K_ow values. This finding indicates that an active transport is responsible for the placental transfer of BPs.

Activation of autophagy inhibits cadmium-triggered apoptosis in human placental trophoblasts and mouse placenta

Cadmium (Cd), a ubiquitous environmental pollutant, is known to impair placental development. However, the underlying mechanisms remain unclear. The present study used in vivo and in vitro models to investigate the effects of Cd on apoptosis and autophagy in placental trophoblasts and its mechanism. Pregnant mice were exposed to CdCl₂ (4.5 mg/kg) on gestational day (GD) 9. Human JEG-3 cells were exposed to CdCl₂ (0-40 μM) for different time points. Gestational Cd exposure obviously lowered the weight and diameter of mouse placentas. Number of TUNEL-positive cells was markedly elevated in Cd-administered mouse placentas and JEG-3 cells. Correspondingly, Cd significantly up-regulated cleaved caspase-3 protein level, a key indicator of apoptosis, in murine placentas and JEG-3 cells. Simultaneously, Cd also triggered autophagy, as determined by an elevation of LC3B-II and p62 protein, and accumulation of LC3-positive puncta, in placental trophoblasts. Chloroquine an autophagy inhibitor, obviously aggravated Cd-induced apoptosis in JEG-3 cells. By contrast, rapamycin, a specific autophagy inducer, significantly alleviated Cd-triggered apoptosis in JEG-3 cells. Mechanistically, autophagy inhibited Cd-induced apoptosis mainly via degrading caspase-9. Co-localizations of p62, a classical autophagic receptor, and caspase-9 were observed in Cd-stimulated human JEG-3 cells. Moreover, p62 siRNAs pretreatment markedly blocked the degradation of caspase 9 proteins via Cd-activated autophagy in JEG-3 cells. Collectively, our data suggest that activation of autophagy inhibits Cd-induced apoptosis via p62-mediated caspase-9 degradation in placental trophoblasts. These findings provide a new mechanistic insight into Cd-induced impairments of placental and fetal development.

A mechanism for the effect of endocrine disrupting chemicals on placentation

Numerous recent studies have shown that endocrine disrupting chemicals (EDCs) in the body of pregnant women can pass through the placenta and be exposed to the fetus, leading to fetal development and cognitive impairment. Placentation through invasion of trophoblast cells and vascular remodeling is essential to maintaining maternal and fetal health throughout the pregnancy. Abnormal placentation can lead to pregnancy disorders such as preeclampsia (PE) and intrauterine growth retardation (IUGR). However, many studies have not been conducted on whether EDCs can inhibit the development and function of the placenta. Isolating placental tissues to analyze the effect of EDCs on placentation has several limitations. In this review, we discussed the types of EDCs that can pass through the placental barrier and accumulate in the placenta with relative outcome. EDCs can be released from a variety of products including plasticizers, pesticides, and retardant. We also discussed the development and dysfunction of the placenta when EDCs were treated on trophoblast cells or pregnant rodent models. The effects of EDCs on the placenta of livestock are also discussed, together with the molecular mechanism of EDCs acting in trophoblast cells. We describe how EDCs cross the membrane of trophoblasts to regulate signaling pathways, causing genetic and epigenetic changes that lead to changes in cell viability and invasiveness. Further studies on the effects of EDCs on placenta may draw attention to the correct use of products containing EDCs during pregnancy.

Urinary trace metals, maternal circulating angiogenic biomarkers, and preeclampsia: a single-contaminant and mixture-based approach

BACKGROUND

Exposures to toxic metals and deficiencies in essential metals disrupt placentation and may contribute to preeclampsia. However, effects of exposure to combinations of metals remain unknown.

OBJECTIVE

We investigated the relationship between urinary trace metals, circulating angiogenic biomarkers, and preeclampsia using the LIFECODES birth cohort.

METHODS

Urine samples collected during pregnancy were analyzed for 17 trace metals and plasma samples were analyzed for soluble fms-like tyrosine-1 (sFlt-1) and placental growth factor (PlGF). Cox proportional hazard models were used to estimate the hazard ratios (HR) of preeclampsia associated with urinary trace metals. Linear regression models were used to estimate the relationship between urinary trace metals and angiogenic biomarkers. Principal components analysis (PCA) was used to identify groups of metals and interactions between principal components (PCs) loaded by toxic and essential metals were examined.

RESULTS

In single-contaminant models, several toxic and essential metals were associated with lower PlGF and higher sFlt-1/PlGF ratio. Detection of urinary chromium was associated with preeclampsia: HR (95% Confidence Interval [CI]) = 3.48 (1.02, 11.8) and an IQR-increase in urinary selenium was associated with reduced risk of preeclampsia (HR: 0.28, 95% CI: 0.08, 0.94). Using PCA, 3 PCs were identified, characterized by essential metals (PC1), toxic metals (PC2), and seafood-associated metals (PC3). PC1 and PC2 were associated with lower PlGF levels, but not preeclampsia risk in the overall cohort.

CONCLUSIONS

Trace urinary metals may be associated with adverse profiles of angiogenic biomarkers and preeclampsia.

Prenatal Cadmium Exposure Is Negatively Associated With Adiposity in Girls Not Boys During Adolescence

Introduction: Cadmium is a pervasive toxic metal that remains a public health concern and exposure in early life has been associated with growth deficits in infancy and childhood. Growth during adolescence also may be sensitive to effects of cadmium exposure, given the changes in distribution of lean and adipose tissue that vary by sex during puberty. This study examines whether prenatal and concurrent cadmium exposures are associated with adiposity measures at ages 8-15 years in a well-characterized birth cohort. Methods: The sample included 185 participants from the ELEMENT birth cohorts in Mexico City with complete data on urinary cadmium exposures, anthropometry and covariates [child age and sex, household socioeconomic status, and maternal smoking history and body mass index (BMI)]. Maternal third trimester and adolescent urines were analyzed for cadmium using an Inductively Coupled Plasma Mass Spectrometer. Trained personnel obtained anthropometry including height, weight, waist circumference and subscapular, suprailiac, and triceps skinfold thickness. BMI z-scores for age and sex were calculated using the World Health Organization's reference standard. Linear regression models were used to estimate the association of prenatal and concurrent urinary cadmium levels with adolescent anthropometry, adjusting for covariates. Results: Among 87 males and 98 females, median age was 10 years (IQR 9 -11 years). Pregnant women and children had median urinary cadmium concentrations of 0.19 μg/L (IQR 0.12- 0.27 μg/L) and 0.14 μg/L (IQR 0.11- 0.18 μg/L), respectively. Regression models showed inverse relationships between prenatal cadmium exposure and adolescent adiposity. An IQR increase in prenatal cadmium was associated with percent decreases in BMI z-score (-27%, p = 0.01), waist circumference (-3%, p = 0.01), and subscapular (-11%, p = 0.01), suprailiac (-11%, p = 0.02), and triceps (-8%, p < 0.01) skinfold thickness. When stratified by sex, these relationships remained statistically significant in females but not males. Conclusions: Prenatal cadmium exposure was negatively associated with measures of both abdominal and peripheral adiposity in girls, but not in boys. These results emphasize the sex-dependent effects of in utero cadmium exposure on adiposity in adolescence.

Cadmium: Toxic effects on placental and embryonic development

Cadmium is a non-essential trace metal that has strong teratogenic and mutagenic effects in living organisms. The content is more highly enriched in women than in men and can enter the embryo through the placenta and destroy the placenta's morphological structure, resulting in fetal growth restriction. In this report, we review published data linking pregnancy exposure to cadmium to placenta and fetal growth and development toxicity and summarize the related mechanisms. An understanding of how cadmium exposure contributes to placental and fetal development is necessary for the development of prevention and control strategies for fetal development defects caused by cadmium exposure during pregnancy.

Impairment of learning and memory of mice offspring at puberty, young adulthood, and adulthood by low-dose Cd exposure during pregnancy and lactation via GABAAR α5 and δ subunits

Cadmium (Cd) is a pervasive carcinogen and environmental endocrine disruptor. We studied the changes in learning and memory of offspring mice, whose mothers were exposed to 10 mg Cd/L via the drinking water during pregnancy and lactation period, as well as the changes of testosterone and estrogen levels, serum Cd levels, the histopathological changes and the changes in the mRNA and protein levels of different subunits of γ-aminobutyric acid receptor subtype A subunits (G_ABA_ARs) in the hippocampus at the prepuberty, puberty, young adult, and adult stages. At birth, Cd had no obvious effect on mice offspring as statistically accessed based on their body weight, body length, and tail length (all p > 0.05). After grouped, the serum Cd levels increased in the three exposed groups more than in the normal control group at stages (all p < 0.05). Only serum estradiol of female offspring at age 7 weeks was significantly decreased compared with other groups (all p < 0.05). Histopathological results showed that the arrangement of the cells in hippocampal CA1 area of mice offspring was significantly sparse in the exposed groups compared with the control group. At 5 and 7 weeks, two Cd-exposed groups showed prolonged escape latency and exploring time for the platform compared with the normal group in the Morris water maze (all p < 0.05). Only increased protein expression of GABA_ARα5 was found in the Cd group at these two ages. At age 12 weeks, similar impaired learning and memory of female mice, and decreased protein expression of GABA_ARδ was found in Cd-exposed groups. Collectively, low-dose Cd had no effect on the growth of mice offspring but affected their learning and memory, especially female offspring, at puberty, young adulthood, and adulthood through changed structure in the hippocampal CA1 area and protein expression of GABA_ARα5 and GABA_ARδ.

Placenta-specific 9, a putative secretory protein, induces G2/M arrest and inhibits the proliferation of human embryonic hepatic cells

Background: Placenta-specific 9 (Plac9) is a putative secreted protein that was first discovered in the context of embryogenesis. The expression pattern of Plac9 during embryogenesis, together with the results of recent reports, suggest that Plac9 may play a role in the liver development. The present study was conducted to investigate the secretory characteristics of Plac9 and its potential role in liver cell physiology. Methods: Immunofluorescence was employed to identify the subcellular distribution of Plac9. Cellular proliferative activity was analyzed by MTT assay and cell colony formation. The cell cycle distribution of Plac9 was analyzed by flow cytometry, and a functional analysis was performed using L02 cells following their stable infection with a lentivirus over-expressing Plac9. Results:Plac9 is a novel protein that is localized to the cytoplasm and may be secreted through the classic endoplasmic reticulum-Golgi route. The overexpression of Plac9 inhibits cell growth and induces G2/M phase arrest. Conclusion: Our findings reveal a novel role for Plac9 in regulating cell growth.

TiO2 nanoparticles enhance bioaccumulation and toxicity of heavy metals in Caenorhabditis elegans via modification of local concentrations during the sedimentation process

Unintentionally released titanium dioxide nanoparticles (TiO₂ NPs) may co-occur with pre-existing heavy metal pollutants in aquatic environments. However, the interactions between NPs and heavy metals (HMs) and their co-effects in living organisms are largely unknown. The aim of this investigation was to illustrate the influence of TiO₂ NPs (5 and 15 nm) on the bioaccumulation and toxicity of cadmium (Cd), arsenate (As(III)), and nickel (Ni) in Caenorhabditis elegans (C. elegans) during the process of sedimentation in aquatic environment. Our data showed that HMs accelerated the aggregation of TiO₂ NPs. The rapid aggregation and sedimentation of TiO₂ NPs changed the vertical distribution of HMs through adsorption and induced increased and prolonged exposure of benthic species. Aggregate particle size along with ionic strength were the major factors affecting the rate of sedimentation. TiO₂ NPs at non-toxic concentrations efficiently enhanced the bioaccumulation and reproductive toxicity of HMs to C. elegans in a dose- and size-dependent manner; however, the effect of TiO₂ NPs on As(III) was obviously lower than that on two valence metals. These data provided clear evidence that TiO₂ NPs could serve as environmental regulators to significantly facilitate the toxicity and the accumulation of HMs in C. elegans, indicating that the interaction and fate of TiO₂ NPs and HMs on their co-toxic responses during the sedimentation should be considered as a necessary and integral part of risk assessment in the ecological system.

Cadmium-Associated Differential Methylation throughout the Placental Genome: Epigenome-Wide Association Study of Two U.S. Birth Cohorts

BACKGROUND

Cadmium (Cd) is a ubiquitous environmental toxicant that can accumulate in the placenta during pregnancy, where it may impair placental function and affect fetal development.

OBJECTIVES

We aimed to investigate Cd-associated variations in placental DNA methylation (DNAM) and associations with gene expression; we also aimed to identify novel pathways involved in Cd-associated reproductive toxicity.

METHODS

Using placental DNAM and Cd concentrations in the New Hampshire Birth Cohort Study (NHBCS, n=343) and the Rhode Island Child Health Study (RICHS, n=141), we performed an epigenome-wide association study (EWAS) between Cd and DNAM, adjusting for tissue heterogeneity using a reference-free method. Cohort-specific results were aggregated via inverse variance weighted fixed effects meta-analysis, and variably methylated CpGs were associated with gene expression. We then performed functional enrichment analysis and tests for associations between gene expression and birth size metrics.

RESULTS

We identified 17 Cd-associated differentially methylated CpG sites with meta-analysis p-values<1×10⁻⁵, two of which were within a 5% false discovery rate (FDR). DNAM levels at 9 of the 17 loci were associated with increased expression of 6 genes (5% FDR): TNFAIP2, EXOC3L4, GAS7, SREBF1, ACOT7, and RORA. Higher placental expression of TNFAIP2 and ACOT7 and lower expression of RORA were associated with lower birth weight z-scores (p-values<0.05).

CONCLUSION

Cd-associated differential DNAM and corresponding DNAM-expression associations were observed at loci involved in inflammatory signaling and cell growth. The expression levels of genes involved in inflammatory signaling (TNFAIP2, ACOT7, and RORA) were also associated with birth weight, suggesting a role for inflammatory processes in Cd-associated reproductive toxicity. https://doi.org/10.1289/EHP2192.

Maternal exposure to selenium and cadmium, fetal growth, and placental expression of steroidogenic and apoptotic genes

BACKGROUND

Cadmium (Cd) and selenium (Se) antagonistically influence redox balance and apoptotic signaling, with Cd potentially promoting and Se inhibiting oxidative stress and apoptosis. Alterations to placental redox and apoptotic functions by maternal exposure to Cd and Se during pregnancy may explain some of the Cd and Se associations with fetal development.

OBJECTIVES

Investigate associations between Cd and Se concentrations in maternal toenails with placental expression patterns of tumor necrosis factor (TNF) and steroidogenic genes involved in redox reactions and test associations with fetal growth.

METHODS

In a sub-sample from the Rhode Island Child Health Study (n = 173), we investigated the relationships between: (1) maternal toenail Cd and Se concentrations and fetal growth using logistic regression, (2) Cd and Se interactions with factor scores from placental TNF and steroidogenic expression patterns (RNAseq) using linear models, and (3) TNF and steroidogenic expression factors with fetal growth via analysis of covariance.

RESULTS

Se was associated with decreased odds of intrauterine growth restriction (IUGR) (OR = 0.27, p-value = 0.045). Cd was associated with increased odds of IUGR (OR = 1.95, p-value = 0.13) and small for gestational age (SGA) births (OR = 1.46, p-value = 0.11), though not statistically significant. Cd and Se concentrations were antagonistically associated with placental TNF and steroidogenic expression patterns, which also differed by birth size.

CONCLUSIONS

Se may act as an antagonist to Cd and as a modifiable protective factor in fetal growth restriction, and these data suggest these effects may be due to associated variations in the regulation of genes involved in placental redox balance and/or apoptotic signaling.

Chromium VI - Induced developmental toxicity of placenta is mediated through spatiotemporal dysregulation of cell survival and apoptotic proteins

Environmental contamination with hexavalent chromium (CrVI) is a growing problem both in the U.S and developing countries. CrVI is a heavy-metal endocrine disruptor; women working in Cr industries exhibit an increased incidence of premature abortion and infertility. The current study was designed to understand the mechanism of CrVI toxicity on placental cell survival/death pathways. Pregnant mothers were treated with or without CrVI (50ppmK₂Cr₂O₇) through drinking water from gestational day (GD) 9.5-14.5, and placentas were analyzed on GD 18.5. Results indicated that CrVI increased apoptosis of trophoblasts, vascular endothelium of the metrial glands and yolk sac epithelium through caspase-3 and p53-dependent pathways. CrVI increased apoptosis in labyrinth and basal zones in a caspase-3-independent manner via AIF, and through an ATM-p53-NOXA-PUMA-p27 network. CrVI downregulated cell survival proteins Bcl-2, Bcl-XL and XIAP in the placenta. CrVI disrupts placental histoarchitecture and increases cell death by spatiotemporal modulation of apoptotic signaling.